Airlines have expressed frustration at the problem which came just days after Nats published an initial report into a "software defect" which impacted air traffic control operations on 8 September.

Nats chief executive Martin Rolfe told BBC News he would not resign, saying the software defect was "very, very obscure".

Ryanair said the latest issue had impacted 140 of its flights and 25,000 passengers, and called on Rolfe to quit.

Ryanair's chief operations officer, Neal McMahon, said: "Just three days after Nats assured airlines and passengers that it had introduced robust 'mitigation plans', its flight data processing system has failed again.

"Martin Rolfe's report claimed that another failure was 'unlikely' and that Nats could recover more quickly if one occurred. Those claims have been exposed as completely worthless.

"Just three days later, passengers are once again suffering lengthy delays because Nats has failed to deliver either a reliable system or an effective back-up."

He called for Rolfe to resign or be removed from his position.

Steve Heapy, chief executive of Jet2, said customers being let down again was "simply not good enough".

He said: "Once again, airlines and customers are being disrupted by yet another Nats issue, and one has to ask: how many more failures do customers and airlines have to deal with.

"Customers work hard to look forward to their holidays, and airlines work hard to deliver those holidays. They should not be repeatedly exposed to delays and disruption because the UK's air traffic control systems cannot be relied upon."

British Airways said it was "disappointing" that some customers may experience disruption after "yet another technical fault with Nats".

Nats is the UK's leading provider of air traffic control services and handles about 2.5 million flights per year.

This is the fourth national air traffic incident in the past three years.

In 2023, a computer shutdown over the August bank holiday weekend caused chaos for 700,000 passengers.

There was another, smaller, Nats outage in 2025 which caused 150 cancellations.

Nats is the UK's leading provider of air traffic control services and handles about 2.5 million flights per year.